Information storage and retrieval system



lIIAONOCHROIYIATIC POINTIJGHT SOURCE MONOCHROMATIC Y POINT LIGHT s OuRCEHOLOCRAAM MONOCHROMATIC f I OBJECT ANO i POINT LIGHT SOURCE OPTICALyVIRTUAL IMAGE 0F OBJECQ s/s AxIs\ Ox/ I n j..

VIRTUSAL IMAGE 'Y VIRTUAL MAGE FROM HoLoGRAM FaxED FOCAL l LENGTH4OPTICAL MovABLE LENs FsxED FOCAL lDI I LENGTH A l l i l l l 1 I l I l Il OPTICAL .AXlSj Ronald H. Kay,'1 aro Ano, cant.,

' i" i .ass/2.1%?"

, misma Maya. 19er tional Business Machines Crporatiomf New -Y *N.Y.,:t4 corporation of New York* f VI-ner Nav. 2s, 195s, No.

v on objects such asl documents. r

The storage of large numbers of documents in a considerable interest,particularly in view of the imc creasing number of documents, such asletters, technical literature, etc., which are accumulating and whoseusefulness depends to a large extent on their read'y accessibility.-Oneofthe systems proposed for the storage of large numbers of suchdocuments Ainvolves the reduci' tion of the documents to a fraction oftheir original l size und the storage of these reduced images on tilmstrips in a storage biu from which they may be retrieved for read-out ofsome sort. Both the recording (posting). of thev document image and thereading' out of the document image involve optical systems employinglenses for producing the desired image transfer. To effect iml agetransfer it is Onecessary that the tilrn strip be positioned a fixeddistance from the image producing leus.

l ,to position a given film strip with respect to the'optical station,thus increasing the complexity of the system and increasing-the timerequired to gain access to any bit z f information in the le.

Broadly, the present invention contemplates an information storage andretrieval system which reduces or eliminates the need for lenses andwhich obviates the movement of the strip with respect to the opticalsys- .tem. The present invention contemplates the storage of the imagesin the form of holograms in a tile system. A hologram is the opticalpattern or image of an object which has both opaque and transparentregions w and which is illuminated by a monochromatic point lightsource. &Jch a hologram has no direct resemblance to' 'the object, butit is the product of a series of overlapping Y ditraction patterns, eachpattern due to a point of the object. A hologram may be produced withoutthe 'aid of lenses and may be permanently recorded on a light sensi- 4tive medium, such as photographiclm. 141; IThis hologram, now atransparency on film. may turn be viewed when illuminated by amonochromatic "point source. The viewed image will constitute a recon-'65 Equation `l and the distance u' of the hologram from.

struction of the original object and can be recorded photographically atthe appropriate position with respect 'to the hologram and the pointsource. In this process, the hologram, which contains all theinformation about the object,is alsocapable ot' performingtheimagelreobject to bc storedix assignor to Interni i invention relatesin generalto, information stor-y b: readily apparentfrom mg followingminion when l f age systems and relates more particularly to systems forthe optical storage and retrieval ci infprmationrecorded an infomationstorage and retrieval system in accordreadily accessible form is aproblem in whichl there is an'ce with the present invention utilizing asingle lens in of the use of reconstructed wavefronts to produce holo-fFig. 3- diagrammatically illuso-attrs the application of .39 Fig. 5 is adiagrammatic illustration of Vrmi-alterna'- This is achieved'by eitherbringing the strip to the imf, rens is related mv the distance and v ofthe hologram 'l ,from the light source and the object, respectively, bytbe ,--whcren is a constant depending the Xgl i.

produced on a suitable light as photographic tilrn. Ilre distance alongthe optical axis 'j `duced and stored at spaced points along the opticalaxis. These holograms constitute the stored. information which may beretrievedfrom the lefand positioned at the same points on the opticalaxis at which the were produced and-illuminated b'y'a monochromaticpointlight source to reproducel 'afacsimilejof the original- .,-lystoredl infomation onsuitable light sensitive output medium.

objects vand advantage ef 'the presagi' wm @read in connection with theaccompanying drawings, 'in

vlhjch: y .-f'.; "f-

1'; Fig.' 1 is a perspective view schematicallyillustratingreconstructing the image from the hologram; V v .i v 'Figs. 2a and 2bdiagrammatically illustrate the theorythe theory of hologram formationto the problem of i11-A formation storage; .1.

y Fig. 4 is `a diagram illustrating the optical facton n volved in theembodiment ofEg. 1; l f

tive embodiment of the-present invention utilizing a lem betdween themonochromatic light source and the object; v.. "Y Fig. 6diagrammatically-illustrates a method of'demagnifying the hologram priorto recording it.'- l Fi'g. 2a illustrates the theory of the use ofrenstructed wavefronts for producing holograms. A s shown in Fig. 2a, amonochromatic point light source S illuminates j E an object o which isspaced a distance d imm the scum S. 1 -'he diffraction pattern resultingfrom this illumination falls upon a sheet of light sensitive materialIL'such4 .i

i' as a film strip, to form thereon s hologram of the object "Si ages,O'an-:l 0", of the original object'. These two ages may be both virtualor one of them, namely, th-Q conjugate image 0', may be -r'eal'dependingupon the geometrical 'arrangement employed in making and rb iconstructing the hologram. The hologramA thus not: simultaneously as Vapositive and a negative lens with a i builtin object. The focal length fof this equivalent""" Qwns. se

measured along the hologram .and l is the wavelength of theillumination. used in making thc hologram. From g" the source during theprocess of reconstruction;

v', 5v". of theitwo reconstructed images O', 0"; lm. from the hologramcan'be'ealculatedfrom the follow- *Y when the symbols viceversa.

above.

by nl meral 12.

I :T1-f I 4.(4). of this method er image formation is innite. In otherwords, a hologram contains all the information'ol' a'thick object. Sincethere is a specific relationship between a'ny plane in the object andits Y reconstruction, it appears that any plane can be recon s tructedat will. interference from other 'planes' willbe 'serious only when thedepth of focusof the "hologram is large compared these reconstructedplanes; lThe magnification ofthe reconstructed -image is the product ofthe geometrical and the physical magnificaf tion. The geometricalmagniiication is determined from the distances u, v, uf and v', whilethe physical magniiication is determined from the wavelengths oi the'-'gradiations A and l.' used for making and reconstructing' v thehologram. Equation?. shows that' if f is to be constant, and A increasesto A', thenvXn should be increased I to Xn, resulting in .increasing thegeometrical magnication by the factorrVTX. On the other hand, ifXn isleft constant, then an increase in )t will result in' a deffge'i fil)15"? (ufd1(ft l hav-el the same meaning as in Figs. 2aand2b.

Fig. 3 diagrammatically illustrates the application of the theory ofhologram formation to' the problem of document storage. A monochromaticpoint source S illuminatesa partially transparent object which mayresulting the illumination of obiect '1'1 source 16 fails upon a strip22 of alight may be of any suitable type which is sensitive to the light'from source 16 to produce the designed hologram.- Bxamples of suitablematerials would includevesicnlar materials which are responsive toultraviolet light followed4 crease in f and hence the tnal magnificationwill be thes -'geometrical one only. The totalmagnication m can 25 becalculated from the formula:

print-out 'or dry processed radiation sensitiv, material on 'I IO -tothe separation between x21'. 21", Za plurality of strips 22,22', etc.may be crease the capacity of the storage system.

yifohject 11. Such positioning",; o`fstrip 22 may be perwhich thehologram is to be produced. Such medium by heat, or the Chakley type ofmaterials, orany other aitransparent base. sA- number of separate 2l,yetc-maybe recorded' on each strip In the embodiment illustrated n Fig.i1, each of strips 22, 22',- etc. may be positioned to ali'gn'jthedesired'image locations 21, 21', 21"', etc. on the selected strip 22along the optical axis with'the-light source 16and 'the formed` by anysuitable means such as oneincluding an arm 26 which is positionable togrip the top of a selected strip 22 and withdraw this strip acontrollable distance from a storage bin27. Storage bin 27 holds a'plurality 'of the strips 22, with each of the strips fitting in acorresponding slot in the bin and being spaced from -the other A stripsalong the optical axis. For production of a hologram cedure is asfollows. The object 11 to be stored is positioned by mechanism 12 infront of the monochromatic Y point light source 16 on the optical axisdiscussed above.

" the desired one of image locations 21 within this selectkrepresent adocument to be stored in the system. This illumination of the objectwill form a hologram H, from which two images, O and O' can bereconstructed. The document thus can bc stored in the form of hologramH, while it can be read outin either the plane 0 or l the plane O'. Obeing the virtual image while 0 is the Areal image.

' have a magnication higher than unity. lt is necessary in the documentstorage system under consideration that ed'strip is positioned en theoptical axis to receivethe diffraction .pattern resulting from theillumination of object 11 by source 16. A shutter 23 may control the ex.posure of image location 21 on strip 22.. Thediraotion pattern fallingon the selectively positioned image "of the obieeru ma 1"' f -zthestorage of this hologram in the le system, the pro- (5) location ofstrip 22 thus produces thereon a hologram ofA the object 11 whichcomprises the file image for storage. the case of a print-out emulsion,no further processing of the light sensitive material is required. Inthe case of a heat developed material, such as vesicular materials, asource of infra-red radiation may be focused the holograms of diierentobjects be stored in different planes, wlLile the tinal readable imagesshould be in the `s'arne plane. In other words, it is required that v isvariable for different objects while (v-Jf-v) is constant.

"I 'Q accomplish the above requires that the virtual image O be utilizedand Ithereal image 0' '.\be eliminated, or

Fig. l illustrates in perspective form one suitable sys- -tem fordocument storage by means of holograms in ac- 'cordance with thetheoretical 'considerations discussed Reference numeral 11 designates anobject, an image of which isto be stored in the system'of the presentinvention.- Object 11 may be a transparency or microfilm, positive ornegative, of a letter or printed pageor drawing or any other documentwhich is to be stored for subsequent retrieval. Objt 11 will have opaqueY may be positioned with respect to the optical Yaxis 'by lm drivedesignated means of a mechanism such as the Object 11 is ill productionof the hologram and the reconstruction there-1 of, 1t is necessarytoutilize a lens 31 in reconstructing.

ony the exposed tilm strip to e'ect heat development. Upon completion ofproduction of the hologram, arm 26 lowers the withdrawn strip 22 bckintoits slot in bin 27 vwhere the image may be stored until reproduci iftion thereof is desired.

When` it is desired to 1l from the selected location 21 on strip 22, arm26 again withdraws the selected strip 22 from bin 27 and again positionsthe strip so that location 21 containing` their-nage -obj-ect v if theimage of object 11 is positioned along the optical' axis. Under thesecircumstances, of course, object 11 will not be positioned in front oflight source 16. If

all the elements of the optical system of the embodiment .i

ofvFi'gl l are to befmaintained stationary during both the theimage fromthe stored hologram. The optical'vxri` ables involved in the apparatusillustrated in Fig. 1 are shown diagrammatically in Fig. 4, where Srepresents the l lines labeled holograms."` When a hologram on one ofvstrips 22 is image,.a virtual image of the hologram will be formed inPlane C ofliig. 4. Lens 31 is positioned as shown in Flgs 4 to form animage of this virtual image of plane" 1-" uminated by of a.. pointsource 16 of monochromatic radiation such-as the lamp 16a andmonochrrmatrc filter 161:.

The diffraction patternv sponsive to the illumin 0 plane O1, and it isin this plane O1 that the outputmCdlUm i5 disposed on whiclra facsimileof the stored '1- may be of any suitable photosensitive type which isreation from lsource 16, and the holograms corresponding to the dierfent strips 22 in hin 2'.' are represented by the vert'Ql-f :informationis'to be produced. 'Such-an Aoutput medium source 16 to produce Ailluminated if. source 16 as discussed above for reconstruction ofthew acopy of the document stored as a hol medium is shown as a strip 32 oflight sensitive material which is disposed in the output plane O1.lStrip 32 may 'they are assumed'to be in this embodiment, the image{reconstructedin plane O will havethe same size-as the tween plane O andthefauxiliarylens 31is twice the `focal length of this lens, the imageinplane O1 will again served as input tothe tile.

.be employed in apparatus similar to that shown in Fig. l

and diagrammatically represented in Fig. 4, let-the spac- For anotherobject having a hologram Hn, let, l

u=52ctxt'.A

vn=36 cm.

storage space available is then 52-2 0=3?. cm. Reeon struction of theimages may be achieved with a posi- It will be seen that the embodimentillustrated in Fig.

1 resultsv in a system in which each of the strips 22 need be moverlonly in a vertical direction to position t the desired one of imagelocations 21 on the optical axis with the monochromatic point lightsource 16 and the light sensitive medium on which the hologram is to berecorded. lt i.. not necessary to move the different strips 22horizontally along the optical axis to position cach of them at the sameoptical station, since the hologram acts as a variable focus lens to4produce an effective foczning of the images on Athe differenthorizontally spaced In the embodiment illustrated in Figs. l end 4, itwas necessary to utilize a lens in the process of reconstructsired toutilize Athe virtually reconstructed image produced in plane O of Fig.4. If it is desired to eliminate lenses completely in a system, it isnecessary to utilize the realreconstructcd image in plane O', as showndiagrammatically in Fig. 3. As discussed above, the reand independent ofvariations in the distance S. lt can be shown that this 'necessitateschanging the distance Ad according to the equation: f .-f 1 2f?.-

A ;=-E -constant the reconstruction of the image recorded` thereon, anychange in the distance between the'object and the hologram must b eaccompanied by a corresponding change in the distance between the objectand the source in such a'way that Equation 5 is satisfied. ln this way,the object plane and the reconstructing plane will be xed for all ogramon strip the di'erent hologram: whichue storedjn diered. 22. In theembodiment illustrated in Fig. l, the output f #i Thus, to employ thepresent utiliz- Fing lenses in either'the formation of the hologram orthe be advanced by means of the reel mechanism illustrated' to receivethe image from the hologramwhich' is stored be at different points alongthe optical axis for In the embodiment illustrated in Figs. and v theholograms. Such' movement ofthe light sottrae 16 source 16 and the'holograms are fixed position. as 10 servopositioning-systemwhichpositions light sour 16 original input-object, so that the finalvmagnication at'A the output stationinA plane. O1 Awill b ej'themagnification producedV by the- -lens.31. '--lf the distance be neouslywith' the vertical' positioning of strip 22 by arm 26 so that thepositioning of the light source does not v-'I `o eliminate the need formoving light source 16, the change in the distance d for the oiterentlhologram-can be achieved by utilizing a lens of fixed focal length Fhave uni'ty magnification. The choice of opticalconliguration andwavelength as indicated in Equation 5 will vfurther aect the size of'thereproduced object' whichv -As a numerical example of the spacigszwhichmight.Y

illustrated in the embodiment of Fig. l, such as ltltc'flight source 16,the object 11, and the strip 22 on which a hologram is formed, arerepresented diagrammatically. '1 3"* 25 .which is movable alongthe'optcal axis in such a way that its distancep from the source 16 isalways less than its -j J vfocal length F. A vittual image S' will thenbe formed equation: f f- In both cases (u-v) =l6 cm.=a constant Thetotal tance for the diterent holograms, the distance may be Y thehologram and then changing the wavelength to a 'i' hologram. Thevariation of wavelength from A to A' C i Y must satisfy the equation:

`This change in wavelength maybe used to particular.

ing the image stored in the hologram, since it was de quirement is that(v+v') should be maintained constant' In other words, during the makingoi 'the holograrnorn planes. i v.

reconstruction thereofA requires vthat the light source-16 differenthologram: so as to satisfy Equation 6 for all of may be performedby anysuitable mechanism, auch as a to any desired position alongfthempticalaxis. This positioning of the light. sordegmay beperformed add anyappreciable tixne to the operation time 'of the which is moved todifferent positions. Su'ch a system is. shown diagrammatically in Fig.5, where the elements This system includes a lens 35 of fixed focallength F whose distance from the object O is d. Changing the dis tancesp or 1 will result in changing d' according to the source and the objectis to bechanged for different holograms. However, as an alternative tovarying this dismaintained constant and the wavelength X of theillumination may be changed. This technique may be utilized in orie formby choosing a value )t during formation of value x' during thereconstruction of the image from the advantage in the case ofphotosensitive materials which are light sensitive to a particularwavelength A, while the exposed regions of the photoscnsiti-ve materialshave a vthat the reconstructed image 0' will always be in thel saineplane. The required variation in the wavelength of the illumination maybe accomplished by any suitable means, such as the interposition ofdiicreat lters for"A c' lter 16h. "a In all oi the above illustrated anddescribed embodi.'" ments the image stored on the hologram'is lager thanthe object itself, owing to the nature of the -formation of holograms.'While it is satsfactoryin many situatiom toV store images which arelarger than the object, .it may be desirable in some situations to forma hologram of rv "i duced size. A method to reduce the size of thestoned;- hologramA involves the optical demagniicatiun of the hologramprior tol recording. In this approach, show-n diagrammatically n Fig. 6,a lens L of short focal length g F is positioned on -the optical axis toproduce images S1, 01 and Hl, respectively, of the source S, the objectO, and the hologram H. H S, O and H are at distances 7i; greater than 2Ffrom the lens, their images S1, C1, and

H, will all be at distances in the -image space which lie between i? and2F from the lens, thus resulting in de `magnication of S1, O1, and H1.The image H1 is re corded, to produce the desired magnication.

` While there have been shown and described and pointout the fundamentalnovel features of the in vention as applied to the preferred embodiment,it will be understood that various omissions and substitutions and.-.schanges in the form and details of the device`l illustrated' 'and inits operation may be made by those skilled in the It is the intention,therefore,to be limited only as cated by the scope o fthefollcwingclaim. What is claimed is:

Apparatus for storing and retrieving images of partially chromatic:light source whch' is substantially .a point sonrtze, a pluralityofstrips of a rstlight'sensitive medi- -um disposed in the differentsaid compartmentsin Said storage'le, means for selectively withdrawingany `one.

-movement in only one dimension to position said selected strip on .anoptical axis with said light source, each of the` vdifferent said stripsbeing positioned at a different fixed 25 exposure point along said axis,meansor disposing said partially transparent object on said optical axisbetween said light source and the light sensitive strip in the ex-lposure position, means for transmitting lightfrom said i ;.'art, withoutdeparting from the spirit of Ythe invention. .ndi`.

transparent objects from a storage. le, said storage filev comprising aplurality of spaced compartments, amonoof said rst light sensitivestrips from said storage tile by le by movement only in said onedimension upon com I sensitive medium, means for positioning said secondmedium on said optical axis at a fixed point along said axis,

'from said storage file by movement .only in said one diaxis betweensaid light source and said second light sensi-- gram nfsaid withdrawnstrip on said second light semi' said object on said hologram, and meansfor returmng said withdrawn' strip to its compartment in said storage,pletion of said reproduction-f "(March 1s, 1956), :Oumar-of The opticalsociety of `America, vol. 46, No. 10, October 1956, pages 825-831.

'souralongsaidaxixtoprodnceoneachofsaidstpsa "7 hologram oi said'pbject,means for returning each said te v moved strip to its respectivecompartment in said storage pletion of the formation of said hologram, asecond light meansfor withdrawing anyone of said exposed strips mensionVto position said withdrawn strip on said optical tive medium, meansforr transmitting light from said source'along said optica; .axis andfor imaging the bolotive medium to producea reproduction of lthe imageof n ,le by movement only in said one" dimension upon com- Referencest'ted .inthe-vle of this patent Um-ran STATES PATENTS .1,263,355 AnigueApr. 16,

" oral-:Rmat-iziuNcr-:s Image Formation by Reconstructed Wave Fronts(sEALi Auen:

corrected below.

' column5, line 53, after "spaced" .insert sigma' andsafledhis'lzzisnhereby appears ntheabove ent requiring correction `and phat the' saidLetters Patent shouldread'as Y lille 30, fOr "l" read -f l line 75, for"Cl" read -..E 201,-;5 r v llifvdyfqf septemberA 1961.

l-4DQAMDLLAJJDf-l" Commissioner of P atcnts uscoMMfoc line 75,101 "C1"read e Ol me UNITEDSTATES PATENT OFFICE CERTIFICATE 0F COIHUCTION PatentNo. 2,982, 176 May 2, 1961 Ronald H., 'Kay vIt is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below..

Column 2, line 14, for "advantagse" column 5, line 53, after "spaced"insert column 6, lines 19, 25, and 28, for "F, read m- F line 30, for"1" read w n1:

u strips 22,'. m; each occurrence, me; same column 6,

Signed and lsealed this 26th day of September 1961,.

(SEAL) Attest:

ERNEST w.sw1DER DAVIDE. LADD Attesting Officer Commissioner of PatentsUSCOMM-DC read a advantages me;

